1. Field of the Invention
The present invention relates to a lens driving device that is mounted in an optical unit (for example, a camera unit of a mobile terminal or an optical pickup mechanism of an optical disc drive) and that is used to focus a lens and to correct spherical aberration of the lens.
2. Description of the Related Art
Japanese Unexamined Patent Application Publication No. 2005-315935 describes an existing technology in this field. According to this Publication, a lens driving device includes a lens holding frame to which a lens is fixed. The lens holding frame includes a first shaft supporting portion and a second shaft supporting portion. A first shaft, which extends through the first shaft supporting portion, prevents rotation of the lens holding frame. A second shaft, which extends through the second shaft supporting portion, enables the lens holding frame to be linearly guided with high precision. A first rack, which rotates around a shaft portion, is attached to the second shaft supporting portion. A rack gear portion, which is formed at an end of the first rack, meshes with a lead screw. The rack gear portion is urged against the lead screw by a torsion coil spring that is wound around the shaft portion. A compression coil spring is wound around a part of the shaft portion between the first rack and a second rack. The compression coil spring urges the rack gear portion in a direction opposite to the second rack along the lead screw, thereby preventing backlash of the rack gear portion.
However, the lens driving device described above has a problem in that the device has a complex structure and a large size, because the device is structured such that the lens holding frame and the rack are rotatably connected to each other through the shaft portion that extends parallel to the second shaft, which is used to guide the lens holding frame with high precision.